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Biogeographia – The Journal of Integrative Biogeography 35 (2020): 1–15 https://doi.org/10.21426/B635043631

New records of Plagyrona Gittenberger, 1977 (: : ) from and problems about specific determination

ENRICO TALENTI, SIMONE CIANFANELLI*, MARCO BODON

Museo di Storia Naturale del Sistema Museale d’Ateneo dell’Università di Firenze, Sezione Zoologica “La Specola”, Via Romana 17, 50125 Florence (), email: [email protected], [email protected], [email protected] * corresponding author Keywords: Mediterranean area, Plagyrona placida, Plagyrona angusta, distribution.

SUMMARY The Plagyrona Gittenberger, 1977, includes only two small species of terrestrial snail: Plagyrona angusta Holyoak and Holyoak, 2012, and Plagyrona placida (Shuttleworth, 1852). While P. angusta is known only from Portugal, P. placida has a vast but fragmented distribution: it is known from some of the Macaronesian islands (Madeira and the Canary Archipelago) and some European countries: Portugal, France (in Corsica only), Italy (including Sardinia and the Tuscan Archipelago), Albania, Greece (in the Ionian Islands only) and North Africa (Algeria). New research has led to redefine the distribution range of P. angusta, identifying new populations in Spain (Balearic Islands), continental France (Var department), southern Italy (), Sardinia and Greece (Kerkyra Island) and to discover new sites of P. placida on Pantelleria island and of Plagyrona spp. in Zannone island and southern Italy. The specific determination of these and others populations by examination of recent literature from Sardinia, Campania and Calabria, was carried out on a morphometric basis, but, for some populations, the variability of the diagnostic characters and the limited number of available specimens, do not allow a precise assignment. On the other hand, the existence of two distinct species is not evident at all, at least in the Mediterranean countries.

INTRODUCTION placida (Shuttleworth, 1852) and P. angusta The genus Plagyrona Gittenberger, 1977, is one Holyoak and Holyoak, 2012. of the six European genera of small terrestrial Plagyrona placida has a fairly large but molluscs belonging to the circumglobal family fragmented distribution (Cianfanelli et al. 2013, of the Valloniidae Morse, 1864, which includes Holyoak and Holyoak 2012, Bank and Neubert about 65 species (Schileyko 1998). The genus 2017), having been reported from the Canary Plagyrona includes two species only: P. Islands (El Hierro, La Gomera, La Palma, Tenerife) (Wollaston 1878, Ibáñez et al. 2001,

Bank et al. 2002, Brito and Fraga 2010), decreasing mesh sieves and the specimens were Madeira (Wollaston 1878, Waldén 1983, Bank visually separated or through a binocular et al. 2002, Cameron et al. 2006, Seddon 2008) microscope. The photographs of the shells were and Porto Santo island (as fossil only; Cameron taken with the light microscope and related et al. 2006), Portugal (Servain 1880, Silva and software. All dimensions (H, shells height; D, Castro 1887, Locard 1899, Gittenberger 1977, shells diameter; h, height; d, aperture Oliveira 2008, 2009, 2010, Torres and Oliveira diameter; U, umbilicus diameter) were 2010), Corsica (Ripken and Bouchet 1998, measured using a micrometer on the light Falkner et al. 2002), Albania (Reischhütz et al. microscope. For the analysis of morphometric 2008, Ferhér and Eróss 2009), Italy, in the data (ratios between the dimensions of the shell Tuscan Archipelago and Sardinia included for describing the differences in shape between (Cianfanelli et al. 2013, Manganelli et al. 2015, the two species: H/D, h/d, U/d, U/H) the Excel 2017) and Greece, in the Ionian Islands of software 2016 (for linear regression curves, for Kerkyra, Ithaki and Kephalonia (Gittenberger the purpose of verifying the isometric or 1989); moreover, it is also known from Algeria allometric model of growth, verifying the best (north-western Africa) (Bourguignat 1863, regression curve in order to apply a correction 1864, Gittenberger 1977). Plagyrona angusta, value to the rations of the parameters for the on the other hand, has been described and specific determination on the basis of the reported in Portugal only (Holyoak and results in literature) and PAST 3.19 (for Holyoak 2012). Principal Components Analysis, PCA, for the In Cianfanelli et al. (2013) a synthesis of purpose of verifying the weight of the the knowledge on the distribution of P. placida diagnostic parameter and how clustering the was carried on, reporting the species collected specimens/populations, and Non-metric multidimensional scaling, NMDS, for grouping for the first time in several Italian localities together the objects (or variables), based on (Sardinia, Campania and Calabria); subsequently Manganelli et al. (2015, 2017) their similarity or correlation, so that the discovered populations of Plagyrona in the elements of a group are as similar as possible to Tuscan Archipelago (Capraia, Elba, each other) were used (Hammer et al. 2001). Montecristo, Giglio islands) and from Monte Data for PCA and NMDS were normalized. Argentario in Tuscany, always identifying them The collection data are listed as follows: as P. placida. This research has ascertained a locality, collection site, altitude, municipality wider distribution for this genus, which was and province/department/region in parentheses, found in Balearic Islands in Spain (Mallorca UTM coordinates (ED 50), denomination of the Island), in southern France (Var department), SCI (a Site of Community Importance, as and in some small Italian islands (Zannone and defined in the European Commission Habitats Pantelleria). The characters that distinguish the Directive, 92/43/EEC), if the locality is inside a two species are not constant and therefore a protected area, collectors and dates, number of morphometric study has been carried out for the shells and collection in parentheses. Names of specific attribution, in order to verify the the localities were taken from the following diagnostic characters and update the maps: for Italy, from the Istituto Geografico geographical distribution of these taxa. Militare 1:25,000 chart; for France, from Institut Géographique National 1:25,000; for Spain, Mallorca, from Kompass 1:75,000 map; MATERIALS AND METHODS for Greece, from the Greek Atlas 1:300,000, Shells were collected in Mediterranean areas of Studio F.M.B. Bologna 1991/92 edition; UTM Spain, France, Italy and Greece, from alluvial coordinates were taken from the same maps or debris or litter; they were sieved using detected by GPS.

2 Biogeographia 35: 1–15 Talenti et al., 2020

Figure 1. Shells of Plagyrona angusta Holyoak and Holyoak, 2012, from France (A), Greece (B-C), Spain (D) and Italy (E- F). A, Gapeau River, downstream the dam near La Clapières, upstream L'Oratoire (Hyères, Var, Provence-Alpes-Côte d’Azur), 32T KN6881, M. Bodon & S. Cianfanelli leg. 29/12/2016 (MZUF GC/52475); B-C, small valley from Lakones to Paleokastritsa (Paleokastritsa, Kerkyra, Ionian Islands), 34S CJ8992, E. Talenti leg. 05/07/1993 (MZUF GC/45670); D, Torrent dels Camps, near Can Corlet (Pollenca, Mallorca Island, Balearic Islands), 31S EE0015, M. Bodon & S. Cianfanelli leg. 30/12/2014 (MZUF GC/57153); E, gorge of Bianco River, La Montagnola (, , Campania), 33T WE3395, S. Cianfanelli & E. Talenti leg. 18/05/2014 (MZUF GC/46610); F, mouth of Codula de Sisine (Baunei, Ogliastra, Sardinia), 32T NK5348, E. Talenti leg. 5/07/2017 (MZUF GC/57303).

Talenti et al., 2020 Biogeographia 35: 1–15 3

Figure 2. Shells of Plagyrona placida (Shuttleworth, 1852) (A) and Plagyrona sp. (B-F) from Italy. A, Passo del Kherch near the cave of Brigante, Montagna Grande, Pantelleria Island (Pantelleria, Trapani, Sicily), 33S TA3274, S. Cianfanelli & E. Talenti leg. 30/04/2013 (MZUF GC/43241); B, SSE of Zannone Island above Punta di Levante (Ponza, Latina, Latium); 33T UF3637, S. Cianfanelli & E. Talenti leg. 22/05/2014 (MZUF GC/54665); C-D, Argentino River near Orsomarso (Orsomarso, Cosenza, Calabria), 33S WE7705, S. Cianfanelli & E. Talenti leg. 27/04/1995 (MZUF GC/57182); E, River upstream the confluence of Sciarapotamo Stream, 3 km E (, Salerno, Campania), 33T WE4342, M. Bodon & S. Cianfanelli leg. 05/01/2013 (MZUF GC/42579); F, River 700 m SW from (Auletta, Salerno, Campania), 33T WE3589, S. Cianfanelli & E. Talenti leg. 21/04/1996 (MZUF GC/48110).

4 Biogeographia 35: 1–15 Talenti et al., 2020

The examined material is presently preserved in the following collections: Museo Plagyrona placida (Shuttleworth, 1852) di Storia Naturale dell'Università di Firenze, Sezione Zoologica "La Specola", Via Romana For literature before 2012, see Cianfanelli et al. 17, Florence, Italy (MZUF); M. Bodon, Via (2013). delle Eriche 100/8, Genoa, Italy (MBC); S. Plagyrona placida, Welter-Schultes 2012: 205. Cianfanelli, Via Monferrato 3, Florence, Italy Plagyrona placida, Holyoak and Holyoak 2012: 153- (SCC); E. Talenti, Piazza Parri 4, Figline e 165, Figs. 1 A-C, 3 E-F. Incisa Valdarno, Florence, Italy (ETC). Plagyrona placida, Cadevall and Orozco 2016: 167. Plagyrona placida, Bank and Neubert 2017: 56. RESULTS AND DISCUSSION Plagyrona placida, Welter-Schultes 2018. Systematics Plagyrona placida, Holyoak et al. 2019: 127. Plagyrona angusta Holyoak and Holyoak, Description 2012. Shell (Fig. 2) very small (0.7-1.6 mm in height Plagyrona angusta, Holyoak and Holyoak 2012: 153- (H); 1.0-2.3 mm in diameter (D); 0.2-0.6 mm in 165, Fig. 1 D-F. umbilicus diameter (U); mean ratio H/D = Plagyrona angusta, Holyoak et al. 2014: 45. 0.651 and mean ratio U/D = 0.229; according to Holyoak and Holyoak, 2012, fig. 2), with three Plagyrona angusta, Cadevall and Orozco 2016: 166. to three and a half convex and slowly expanded Plagyrona angusta, Bank and Neubert 2017: 56. whorls, separated by a deep suture; spire not Plagyrona angusta, Holyoak et al. 2019: 127. elevated; last little wide and slightly descending near the aperture. Protoconch not Description protruding, with the surface covered by many Shell (Fig. 1) very small (0.8-1.6 mm in height thin spiral striae and spiral groves, crossed with (H); 1.1-1.9 mm in diameter (D); 0.2-0.4 mm in more spaced and less marked growth lines; umbilicus diameter (U); mean ratio H/D = teleoconch covered by dense periostracal ribs, 0.729 and mean ratio U/D = 0.164; according to clearly visible and equal to each other, and by Holyoak and Holyoak 2012, fig. 2), with three thin spiral lines, sometimes scarcely visible. to four convex and slowly expanded whorls, Aperture roundish, with oblique outer separated by a very deep suture; spire rather peristome, not thickened and not reflected, elevated; last whorl not wide and slightly interrupted in the parietal portion. Umbilicus descending near the aperture. Protoconch not large, corresponding to 3/10 of the maximum protruding, with the surface covered by many shell diameter. Periostracum light brown in thin spiral striae and spiral groves, crossed with colour, with weakly whitish bands, more more spaced and less marked growth lines; evident in not fresh shells. teleoconch covered by dense periostracal ribs, clearly visible and equal to each other, and by thin spiral lines, sometimes scarcely visible. New examined material Aperture roundish, with oblique outer Spain peristome, not thickened and not reflected, interrupted in the parietal portion. Umbilicus - P. angusta: Torrent dels Camps, near Can small, corresponding to 1/6 of the maximum Corlet, alluvial debris, 80 m a.s.l. (Pollenca, shell diameter. Periostracum light brown in Mallorca, Balearic Islands), 31S EE0015, M. colour, with weakly whitish bands, more Bodon & S. Cianfanelli leg. 30/12/2014 (2 evident in not fresh shells. shells, MZUF GC/57153, Fig. 1 D; 7 shells, 2 young shells, SCC).

Talenti et al., 2020 Biogeographia 35: 1–15 5

- P. angusta: Torrent de Son Vic, below La Cianfanelli leg. 01/01/2013 (1 shell, MZUF Granja, debris, 220 m a.s.l. (Esporles, GC/42503; 7 shells, SCC). Mallorca, Balearic Islands), 31S DD6291, - Plagyrona sp.: Tanagro River, 700 m SW M. Bodon & S. Cianfanelli leg. 01/01/2015 from Auletta, alluvial debris, 180 m a.s.l. (1 shell, MBC). (Auletta, Salerno, Campania), 33T WE3589, France SCI “Fiume Tanagro e Sele” (IT8050049), - P. angusta: Gapeau River, downstream the S. Cianfanelli & E. Talenti leg. 21/04/1996 dam near La Clapières, upstream L'Oratoire, (1 shell, MZUF GC/48110, Fig. 2 F). Hyères, alluvial debris, 4 m a.s.l. (Hyères, - Plagyrona sp.: left bank of Landro River, il Var, Provence-Alpes-Côte d’Azur), 32T Ponte, near San Marco, litter in KN6881, M. Bodon & S. Cianfanelli leg. Mediterranean maquies with limestone 29/12/2016 (2 shell, MZUF GC/52475, Fig. rocks, 240 m a.s.l. (, Salerno, 1 A; 2 shells, MBC; 1 shell, SCC). Campania), 33T WE3994, S. Cianfanelli & E. Talenti leg. 18/05/2014 (1 shell, MZUF - P. angusta: Gapeau River, downstream the GC/46601). bridge between Hyères and La-Londe-les- Maures, alluvial debris, 2 m a.s.l. (Hyères, - Plagyrona sp.: Calore River near the Cave of Var, Provence-Alpes-Côte d’Azur), 32T , alluvial debris, 70 m a.s.l. KN6979, M. Bodon & S. Cianfanelli leg. (Auletta, Salerno, Campania), 33T WE1782, 29/12/2016 (1 shell, MBC; 2 shells, MZUF SCI “Alta Valle del Fiume Calore Lucano GC/52475). (Salernitano)” (IT8050002), S. Cianfanelli & Greece E. Talenti leg. 13/10/1994 (1 shell, MZUF GC/50149). - P. angusta: small valley from Lakones to - Plagyrona sp.: Calore River in the bend Paleokastritsa, litter in holm-oak forest at the base of a limestone cliff, 85 m a.s.l. between Case Lucia and Doto, alluvial (Paleokastritsa, Kérkira, Ionian Islands), 34S debris, 75 m a.s.l. (Castelcivita, Salerno, CJ8992, E. Talenti leg. 05/07/1993 (3 shells, Campania), 33T WE1781, SCI “Alta Valle MZUF GC/45670, Fig. 1 B-C; 1 shell, 1 del Fiume Calore Lucano (Salernitano)” (IT8050002), S. Cianfanelli & E. Talenti leg. young shell, MBC; 1 shell, SCC; 13 shells, 26/04/2013 (3 shells, MZUF GC/ 49084). 16 young shells, ETC). Italy - P. angusta: gorge of Bianco River, in locality La Montagnola, litter in Ilex forest, - Plagyrona sp.: at SSE of Zannone Island, 200 m a.s.l. (Buccino, Salerno, Campania), above Punta di Levante, litter in holm-oak, 33T WE3395, S. Cianfanelli & E. Talenti 150 m a.s.l. (Ponza, Latina, Latium); 33T leg. 18/05/2014 (8 shells, MZUF GC/46610, UF3637, SCI “Isola di Palmarola e Fig. 1 E). Zannone” (IT6040020), S. Cianfanelli & E. - Plagyrona sp.: near the cave of Santa Croce, Talenti leg. 22/05/2014 (5 shells, 8 young above , litter in Ilex forest, 620 m a.s.l. shells MZUF GC/54665, Fig. 2 B; 2 shells, SCC). (Ottati, Salerno, Campania), 33T WE2679, SCI “Monti ” (IT8050033), M. - P. angusta: near the cave of San Michele Bodon & S. Cianfanelli leg. 01/01/2013 (3 Arcangelo, litter near limestone rocks in shell, MZUF GC/42383, 10 young shells, Mediterranean maquies, 500 m a.s.l. SCC). (Sant'Angelo a Fasanella, Salerno, Campania), 33T WE2878, M. Bodon & S. - Plagyrona sp.: left bank of Mingardo River, Ponte Mingardo, Mediterranean maquies with limestone rocks, 35 m a.s.l. (Celle di

6 Biogeographia 35: 1–15 Talenti et al., 2020

Bulgheria, Salerno, Campania), 33T literature reports cases where the species have WE3037, SCI “Fiume Mingardo” been found alive (Holyoak and Holyoak 2012): (IT8050013), M. Bodon & S. Cianfanelli in rocky habitats or trees, trunks and branches leg. 05/01/2016 (1 shell, SCC). covered by mosses, in the Mediterranean scrub, - Plagyrona sp.: Bussento River upstream the in holm oak forests or in mesophilic deciduous forests. Even in Italy, Plagyrona has almost confluence of Sciarapotamo stream, 3 km E always been found in intact environments, Torre Orsaia, alluvial debris, 45 m a.s.l. (Morigerati, Salerno, Campania), 33T some of which are included in Sites of WE4342, SCI “Basso corso del Fiume Community Interest (SCI), in Campania, in the Bussento” (IT8050007), M. Bodon & S. Alburni Mountains and in the , in the Cianfanelli leg. 05/01/2013 (1 shell, MZUF Mediterranean scrubs with vast limestone rocky outcrops, and mostly in the mature holm oaks GC/42579, Fig. 2 E; 3 shells, SCC). both on Zannone and Pantelleria islands. For - Plagyrona sp.: Argentino River near example, on the highest elevation in Pantelleria, Orsomarso, alluvial debris, 100 m a.s.l. Montagna Grande (Fig. 3), there is a wet holm (Orsomarso, Cosenza, Calabria), 33S oak, with a microhabitat formed by mosses and WE7705, SCI “Valle del Fiume Argentino” lichens abundant on the trunks and branches, (IT9310023), S. Cianfanelli & E. Talenti leg. which recalls that of the laurel forests in 27/04/1995 (2 shells, MZUF GC/57182, Fig. Macaronesia islands. 2 C-D).

- P. angusta: mouth of Codula de Sisine,

alluvial debris, 0 m a.s.l. (Baunei, Ogliastra, Sardinia), 32 T NK5348, E. Talenti leg. 5/07/2017 (1 shell, MZUF GC/57303, Fig. 1 F). - P. placida: Passo del Kherch near the Brigante cave, Montagna Grande, Pantelleria Island, litter in Ilex forest, 820 m a.s.l. (Pantelleria, Trapani, Sicily), 33S TA3274, SCI “Isola di Pantelleria: Montagna Grande e Monte Gibele” (ITA010019), S. Cianfanelli & E. Talenti leg. 30/04/2013 (1 shell, 1 young shell, MZUF GC/43241, Fig. 2 A).

Habitat The research was conducted by collecting organic substrate (litter or alluvial debris), where no alive were found, but only empty shells were extracted. Despite this, it was ascertained that the material was freshly deposited. The shells originated from the habitats near the collection sites, even if it was not possible to define with certainty the Figure 3. Collecting site of Plagyrona placida microhabitat where the specimens lived. The (Shuttleworth, 1852) in Pantelleria Island, Sicily, Italy.

Talenti et al., 2020 Biogeographia 35: 1–15 7

Figure 4. Distribution of populations of Plagyrona spp. in Macaronesia, Europe and northern Africa. Plagyrona placida (Shuttleworth, 1852), recent (green triangles), fossil (green triangles with asterisk); Plagyrona angusta Holyoak and Holyoak, 2012 (yellow squares); Plagyrona spp. (red dots).

Distribution and biogeography The new data extend the known distribution of the genus Plagyrona already recorded in Cianfanelli et al. (2013) and confirm a Mediterranean distribution, stretching west to Macaronesia (chorotype according to Vigna Taglianti et al. 1999) (Fig. 4). From a biogeographic point of view, its presence in the islands of the Tuscan Archipelago and in Monte Argentario (Manganelli et al. 2015, 2017) and, based on our data, on Mallorca, in south France, and in Zannone and Pantelleria islands is very interesting. In fact, the presence of Plagyrona in islands - especially of small dimensions - implies a good ability to colonize new areas; this genus is probably transported by birds, as already demonstrated for the genus Figure 5. Principal Components Analysis of the ratios Balea Gray, 1824 (Preece and Gittenberger between the morphometric parameters of the shells in the 2003), with species that shares the same habitat populations of Plagyrona spp. For populations code see of Plagyrona, i.e., trunks of big trees and Table 1. branches covered with mosses.

8 Biogeographia 35: 1–15 Talenti et al., 2020

Remarks about species identity By processing the relations with the While for the historical notes we refer to Principal Components Analysis, the percentage Holyoak and Holyoak (2012) and to Cianfanelli of the variance is 88.1 on the first axis, 6.4 on et al. (2013), a thorough examination of the the second and 5.4 on the third. The parameters data given by Holyoak and Holyoak (2012) and that most influence the PCA are the ratios U/D (loading = 0.6501) and U/H (loading = a comparison of the specimens from the various 0.75279) on the first axis (perhaps may be populations for a definition of the diagnostic characters, which may allow distinguishing the weekly correlated with the dimensions of the two species, is necessary. shells, see below, regression curve), h/d (loading = 0.82443) on the second axis and H/D Holyoak and Holyoak (2012) affirm that (loading = 0.68041) on the third axis. the shells of the two species are always Therefore, the ratios relating to the diameter of identifiable if exceeding 1.5 mm in breadth and the umbilicus would be the parameters of the two species can live sympatrically without greater importance than the ratios relating to the showing any intermediate specimens. height/diameter of the shell or of the opening. According to Holyoak and Holyoak Figure 5 shows a prevalent distribution of the (2012), the discriminating characteristics points on positive values of the first axis (broad between the shells of the two species are: umbilicus with respect to the diameter or height of the shell), such as those from the P. placida: Perdasdefogu population in Sardinia of and Lao D max 2.30 mm (largest shell in diameter); River in Calabria, while on negative values of PC1 and positive of PC2 (narrow umbilicus and H/D= 0.586-0.511; 0.651 average (spire greater height of the mouth or of the shell) are more flattened); located the populations from Kerkyra, Greece U/D= 0.171-0.290; 0.229 average (wider and from Var, France. However, for the umbilicus); populations represented by a certain number of specimens, a strong dispersion is noted and less deeper sutures. therefore variability in relationships. Moreover, P. angusta: there is no clear concentration of the points that D max 1.95 mm (smaller shell in diameter); can confirm the existence of two or more distinct species. Even through Non-metric H/D= 0.658-0.854; 0.729 average (higher Multidimensional Scaling, the result is similar. spire); Based on the data of Holyoak and U/D= 0.125-0.198; 0.164 average (narrower Holyoak (2012), the H/D and H/U ratios do not umbilicus); exactly follow a linear regression curve, but the deeper sutures. equation that best correlates the trend is represented by an exponential curve (R² always Due to the lack of an evident growth stop in higher than a straight line, in both cases, for adult shells, the D max character is useful to both species) (Fig. 6). Therefore, the H/D and recognize adult shells of P. placida, since this H/U ratios are not constant, but vary with the species reaches larger dimensions; for P. size of the shell, according to the exponential angusta this parameter is less useful and can be formula: H = 0.3088e0.8224D and H = used only if it is possible to examine several 0.0531e0.9879U for P. angusta, H = 0.3526e0.6578D shells, probably including adult specimens. The and H = 0.0756e0.9286U for P. placida. For each depth of the sutures is difficult to quantify, specimen, calculating on the basis of these while the relationships between H, D and U are exponential formulas, from the parameters characters that are useful for the morphometric “diameter D” and “umbilicus U”, the theoretical analysis. Talenti et al., 2020 Biogeographia 35: 1–15 9

dimension H for P. angusta and for P. placida, Perdasdefogu (Sardinia) and Lao River and comparing this value with the real (Calabria) specimens. Where the values of the dimension H, it is possible to evaluate the two parameters denote a concordance and deviation respecting the theoretical regression therefore the attribution to one of the two curves, and therefore have an indicative value, species, on the other side, in many instances, useful for the attribution of the specimen to one the variability or the intermediate situation do or the other species. In Table 1 the deviation not allow the certain identification. In these refers to the middle point between the two cases, it would be necessary to examine curves and it is expressed in percentage (%), additional specimens in order to better study the with respect to the distance between the curve variability or to check whether the two distinct that represents the average between P. angusta taxa are present in sympatry. and P. placida, with the curves of the respective However, it is important to note that species, with positive values if closer to P. both the PCA analysis and the analysis using placida, negative if closer to P. angusta. So a the regression curves have provided comparable value of 0% means that the parameter H (or the results. It would also be important to verify parameter U) falls exactly in the middle other populations, such as those of the Tuscan between the curves of the two species, + 50% if Archipelago, where, at least for Capraia island, it falls closer to the curve of P. placida ¼ than based on the published illustrations (Manganelli compared to ¾ from P. angusta, + 100% if it et al. 2015), the shape of the shell would seem falls exactly in the curve of P. placida, + 200% to belong to P. angusta rather than P. placida. if it falls beyond the curve of P. placida at a distance equal to twice the distance between the two curves (and therefore much more distant 0.7 y = 0.0756e 0.9286x from the curve of P. angusta). Similarly, but on R² = 0.9344 negative % values, if the H and U parameters 0.6 are closer to the P. angusta curve.

Examining the results (Table 1), since 0.5 the H/D and H/U correlations do not follow a linear trend but vary with size, some

U 0.4 relationships give a very different result based y = 0.0531e 0.9879x R² = 0.8767 on the exponential correlation. For example, the 0.3 average H/D between the populations of R² = 0.8884 Mallorca and Sardinia (Perdasdefogu) has the same value, while the result, based on the 0.2 exponential correlation, attributes the two R² = 0.8583 populations to two different species. However, 0.1 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 there is a strong variability within populations, D P. angusta P. placida with values often close to the value limit linear (P. angusta) exponential (P. angusta) between the two species or also discordant linear (P. placida) exponential (P. placida) between the two series of H/D and H/U ratios.

Whereas the specimens are quite numerous, and there are no strong variations in the parameters, Figure 6. Linear and exponential regression curves based it is possible to attribute them: to P. angusta for on H/D (7 A) and H/U (7 B) ratios based on the data from Holyoak and Holyoak (2012), fig. 2, with the populations from Var, Kerkyra, Mallorca relative value of R2 and the equations of the exponential (although these are a little less high) and for curves. some specimens from Campania (San Michele Arcangelo and Bianco River); to P. placida for

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Table 1. Code and site of the populations of Plagyrona listed in this paper (*: listed in Cianfanelli et al. 2013), with the mean and ± standard deviation of H, D, h, d, U, H/D, U/D and the % of mean shifting H and U (and ± standard deviation shifting), the species attribution and the number of measured shells. The % mean shifting is referred to % distance of H or U from the mean of regression exponential line between P. placida and P. angusta (0%) and the regression exponential line of P. placida (100%) or P. angusta (-100%), calculated by data of D on the bases of regression exponential line by data of Holyoak and Holyoak (2012).

Code Site H D h d U H/D U/D % shifting H % shifting U Species N° shells

ES-MI Spain Mallorca Island 1.02 1.49 0.59 0.70 0.24 0.69 0.16 -52% -74% P. angusta 7 ±0.07 ±0.07 ±0.06 ±0.06 ±0.02 ±0.03 ±0.02 ±86% ±70% FR-GR France Gapeau River 1.23 1.64 0.63 0.73 0.29 0.74 0.18 -119% -57% P. angusta 6 ±0.25 ±0.18 ±0.06 ±0.09 ±0.07 ±0.08 ±0.02 ±95% ±56% GR-KI Greece Kerkyria Island 1.35 1.75 0.71 0.78 0.31 0.77 0.18 -183% -65% P. angusta 9 ±0.14 ±0.13 ±0.04 ±0.06 ±0.03 ±0.03 ±0.01 ±42% ±49% La-ZI Lazio Zannone Island 1.20 1.69 0.58 0.73 0.34 0.71 0.20 -53% +53% P. sp. 2 ±0.04 ±0.02 ±0.04 ±0.03 ±0.00 ±0.01 ±0.00 ±25% ±3% Cp-ML Campania Massa Lubrense* 1.16 1.68 0.70 0.77 0.30 0.69 0.18 -12% -53% P. sp. 1 Cp-SA Campania Sant'Angelo a F. 1.13 1.58 0.63 0.76 0.26 0.71 0.16 -92% -83% P. angusta 4 ±0.06 ±0.06 ±0.03 ±0.04 ±0.02 ±0.01 ±0.01 ±20% ±17% Cp-TR Campania Tanagro River 1.28 1.93 0.79 0.84 0.38 0.66 0.19 +78% -62% P. sp. 1 Cp-LR Campania Landro River 0.91 1.53 0.61 0.79 0.23 0.59 0.15 +196% -135% P. sp. 1 Cp-CR Campania Calore River 1.39 1.98 0.76 0.89 0.46 0.70 0.23 +24% +43% P. sp. 3 ±0.11 ±0.22 ±0.08 ±0.11 ±0.13 ±0.03 ±0.04 ±101% ±83% Cp-BR Campania Bianco River 1.19 1.62 0.62 0.75 0.26 0.73 0.16 -124% -102% P. angusta 5 ±0.10 ±0.10 ±0.05 ±0.07 ±0.03 ±0.02 ±0.01 ±35% ±54% Cp-OT Campania Ottati 1.15 1.61 0.62 0.82 0.30 0.71 0.18 -75% -3% P. sp. 3 ±0.15 ±0.11 ±0.03 ±0.11 ±0.04 ±0.05 ±0.01 ± 89% ±27% Cp-MR Campania Mingardo River 1.26 1.85 0.79 0.86 0.45 0.68 0.24 +36% +158% P. sp. 1 Cp-BR Campania Bussento River 1.35 1.87 0.72 0.75 0.42 0.72 0.22 -18% 60% P. sp. 4 ±0.22 ±0.22 ±0.08 ±0.07 ±0.11 ±0.06 ±0.3 ±100% ±63% Cl-AR Calabria Argentino River 1.24 1.77 0.67 0.79 0.37 0.71 0.21 -48% 38% P. sp. 2 ±0.04 ±0.23 ±0.03 ±0.05 ±0.08 ±0.07 ±0.02 ±192% ± 3% Cl-LR Calabria Lao River* 1.25 1.95 0.71 0.82 0.46 0.64 0.24 114% 97% P. placida 3 ±0.05 ±0.13 ±0.08 ±0.01 ±0.11 ±0.02 ±0.04 ±41% ±103% Sa-PE Sardinia Perdasdefogu* 1.40 2.04 0.77 0.88 0.51 0.69 0.25 +59% +56% P. placida 15 ±0.11 ±0.17 ±0.07 ±0.06 ±0.10 ±0.03 ±0.03 ±63% ±90% Sa-CS Sardinia Codula Sisine 1.03 1.50 0.56 0.64 0.19 0.70 0.13 -91% -216% P. angusta 1 Si-PI Sicily Pantelleria Island 1.34 1.98 0.73 0.88 0.46 0.68 0.23 +68% +62% P. placida 1

CONCLUSIONS species introductions is very unlikely. The discovery in Italy of new Plagyrona sites, Therefore, on the basis of the collected with the first report of P. placida (Shuttleworth, elements, Plagyrona species are considered 1852) for a new locality (Sicily), and the first indigenous elements in all the collection sites. reports of P. angusta Holyoak and Holyoak, The specific identification of the various 2012, in Spain, France, Greece and Italy populations has been carried out on a (Campania and Sardinia), are the result of morphometric basis, but, for some populations researches on the distribution of Palaearctic (see Table 1), the variability of the malacological fauna, not targeted but extended discriminating characters and the limited to many Italian and European areas. number of available specimens, are facing a difficult certain assignment. On the other hand, The fact that the distribution of these two species was underestimated due to their from the analysis carried out, confirmation of small size, their habitat, their mimicry and to the existence of two distinct species is not at all the fact of being rare and localized, had already evident, at least in the Mediterranean countries. been highlighted by Cianfanelli et al. (2013). The genital tract of Plagyrona is still unknown; in the Valloniidae the aphallia is frequent Moreover, the species can be confused with (Giusti et al. 1995, Schileyko 1998). In this other small terrestrial gastropods, such as those of the genera Fitzinger, 1833, case, the reproduction by parthenogenesis could Iredale, 1913, or Beck, express distinct morphological clones; a genetic 1847; also for this reason only recently the analysis could therefore clarify the present genus Plagyrona has been reported in Italy and status of the European populations. Unfortunately, the failure to find living in other Mediterranean European countries. For specimens has so far prevented to carry out example, in the Alburni Mountains (Campania, Italy), a recent and detailed research on the anatomical and genetic research on these terrestrial molluscs of this area (Maio et al. species. 2017), does not report its presence, when, instead, Plagyrona is present.

The doubt that P. placida may be a ACKNOWLEDGEMENTS cryptogenic species, accidentally introduced by man in Italy, was expressed in Cianfanelli et al. We thank Emanuele Bodon, Antonio Braccia, (2013), but the new collected data are further Micaela Calcagno, Elisabetta Lori, Emma and increasingly substantial elements to Santini, Gabriella Vezzani, for their help during consider this species as autochthonous, thus the research and Gianna Innocenti for revising excluding a passive anthropic diffusion as the translated manuscript. Research was already occurred for other small terrestrial partially funded by contributions of the species. For example, Museum of Natural History of Museum System (Shuttleworth, 1852), scintilla (Lowe, of University of Florence, Zoological Section 1852), (Pilsbry, 1890) are “La Specola”. common species almost everywhere in the alluvial debris along the rivers (Cianfanelli et al. 2007), but if we exclude a site near a cave (Sant'Angelo a Fasanella), where Paralaoma REFERENCES servilis is present, no alien species were Bank, R.A. & Neubert, E. (2017) Fauna Europaea collected in all the other litter samples. Many of Project. Checklist of the land and freshwater these sites are intact environments, far from Gastropoda of Europe. Last update: July 16th, inhabited sites, where the chance of non-native 2017.

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